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Dura Ace threadless headset, Help "Atombomber"(6 posts)

Dura Ace threadless headset, Help "Atombomber"thdrk1
Jul 11, 2002 7:27 PM
Team Mapei and Rabobank continue to use Dura Ace headsets converted to threadless and I want one. Why you ask, just to make a replica race bike. "Atombomber" posted in August 2001 that he converted 4 of them using a lathe. Atombomber if you are out there I will pay you for one. Does anyone know where I can get one or have it made. I found one in England at a good shop and tried to install it, but it bottomed out before touching the bearing. I suppose it was generic and not meant to work with Shimano. The photo is from Cyclingnews
Thanks for any help.
easy....C-40
Jul 12, 2002 1:45 PM
Just take a round file and file out the threads on the top cap and toss the locknut. A lathe is faster and more accurate, though.

Don't understand this: "I found one in England at a good shop and tried to install it, but it bottomed out before touching the bearing." What bearing would that be? If you install a new headset, you replace everything, including the fork crown race.
easy....thdrk1
Jul 12, 2002 4:15 PM
C-40,I should have been more descriptive. The part I bought in England was just the top race with a conical compression ring with a slit. The aluminum race looked fine and when I got home it matched up pretty well, but inside a conical edge kept it from resting on the bearing. The race created a lot of friction since it was resting against the top headset part inside headtube and not riding on the bearing. In the picture you might be able to tell there is a difference in the center conical, the Dura Ace has a bit of vertical before the conical part, which inhibits it from resting on the bearing, the one on the right is almost all conical. It seems to easy to just file off the threads, because the top race should fit fairly snug against the steerer tube.
I see...C-40
Jul 13, 2002 8:01 AM
The services of someone with a lathe would be the best bet. A lathe could be used to remove the offending portion of the threadless top race that you bought, or remove the threads from the stock DA top bearing race. This sure seems like a lot of trouble though, with so many excellent threadless headsets available at reasonable prices. Machine shop time isn't cheap.

I've had great luck with Campy threadless headsets.
HeyAtombomber
Jul 12, 2002 8:07 PM
I used 1-1/8" XT headsets. They have cartridge bearings, and are not the loose-ball-in-cage type. I have one left, and am saving it for my future 'cross bike.

There are 2 ways you can convert threaded to threadless. I prefer the Aheadset style with the angular compression ring over the King style with just the threads machined out. Using an angular ring, the machining can be less exact, though it is still perfectly round and centered. The King method requires and exact bore to fit over the steerer tube without any play. Raceface and others deal with the precision by adding a recess in the bore of the top cap and positioning a rubber O-ring to take the slack out.

Use your yellow pages and find a machine shop that does one-off items. Take the upper race and the aluminum Aheadset angular compression ring (which you aquired from a bike shop's spare parts bin) and maybe the fork too and have the machinist lathe out the race such that the compression ring sits about 1mm out of the race. If you want to forgo the comp ring, you will need to take your fork so that the diameter will be exactly matched. Either method should cost you no more than $20 CDN (do the conversion for your currency) for labour, or a case of beer.

Good luck,
AB
Thanks ABthdrk1
Jul 13, 2002 6:36 AM
Thank you for responding. This is such a obscure thing to do I knew there was not much information about it. Right now I am using King headsets, which are almost to tight on the steerer tube. Then I knew I would have a hard time making it myself. So, since I already have the compression ring I will hopefully find a capable machine shop.
Thanks again.